Watt to dBm and dBm to Watt Conversion

What is dBm ?

dBm  is an abbreviation for the power ratio in decibels (dB) of the measured power referenced to one milli watt (mW). It is used in radio and microwave  networks as a convenient measure of absolute power because of its capability to express both very large and very small values in a small value . For example 100Kwatt in dBm can be express as 80dBm and  100 pico watts can be expressed as  - 80 dBm.

Same like dBm there is  dBW, which is referenced to one watt (1000 mW).

Since it is referenced to the watt, it is an absolute unit, used when measuring absolute power. By comparison, the decibel (dB) is a dimensionless unit, used for quantifying the ratio between two values, such as signal-to-noise ratio.

How to Convert Power in dBm and vice versa :

0 dBm equals 1 milli watt. A 3 dB increase in power roughly double the power, which means that 3 dBm equals  2 mW. For a 3 dB decrease, the power is reduced by about one half, making −3 dBm equal to about 0.5 milli watt .

 Power P in watts as m in dBm, or vice versa, the following equivalent expressions may be used:

                  
                   m =  10*Log10 (P*1000)        
                                   or
                    m =  10*Log10 (P) +30                where P is in  watts

and 

         P =  (10 ^m / 10) / 1000                   resultant P is in watts

                           or

        P  =  (10 ^(m-30) /10)

Below is the calculator can be used for the conversion watts to dBm and Vice versa 

Enter a value in Watts and click on calculate to get the value in dBm

• Watts
  Enter value in watts
• Calculate Reset
• Result
  dBm:

  dBm:

Enter a value in dBm and click on calculate to get the value in Watts

• dBm
  Enter value in dBm
• Calculate Reset
• Result
  watts:

  watts:

Some Example of Power in dBm with application are shown in figure :